---
id: CVE-2026-93186
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  cxl/mbox: Clamp mailbox output allocation to the payload size

  CXL_MEM_SEND_COMMAND bounds the user's in.size to the mailbox payload
  size but leaves out.size unbounded,…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  cxl/mbox: Clamp mailbox output allocation to the payload size

  CXL_MEM_SEND_COMMAND bounds the user's in.size to the mailbox payload
  size but leaves out.size unbounded,…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 583fa5e71caeb79e04e477e9837e2f7fa53b71e4 <
    f5d2bbf0300f46307948864fbb97bce5097f4fe2
  - >-
    Linux >= 583fa5e71caeb79e04e477e9837e2f7fa53b71e4 <
    31d4841eca7c4b75751ca96d24339e19303337f2
  - >-
    Linux >= 583fa5e71caeb79e04e477e9837e2f7fa53b71e4 <
    b4e11c731d6bee3b87315e055a1ca417c92dc1fc
  - >-
    Linux >= 583fa5e71caeb79e04e477e9837e2f7fa53b71e4 <
    8a13db9f899d149c3aab24abcb668121cfda5a4f
  - Linux 5.12
published: '2026-09-17'
updated: '2026-09-17'
sourceUpdated: '2026-09-17T17:18:14.683'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-93186'
references:
  - url: 'https://git.kernel.org/stable/c/31d4841eca7c4b75751ca96d24339e19303337f2'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/8a13db9f899d149c3aab24abcb668121cfda5a4f'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/b4e11c731d6bee3b87315e055a1ca417c92dc1fc'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/f5d2bbf0300f46307948864fbb97bce5097f4fe2'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
  - cve.org
ingestedAt: '2026-09-17T16:21:47.726Z'
epss: 0.00209
epssPercentile: 0.09768
---

## Overview

In the Linux kernel, the following vulnerability has been resolved:

cxl/mbox: Clamp mailbox output allocation to the payload size

CXL_MEM_SEND_COMMAND bounds the user's in.size to the mailbox payload
size but leaves out.size unbounded, then cxl_mbox_cmd_ctor() calls
kvzalloc(out.size). A large out.size drives a huge allocation, above
INT_MAX it WARNs and taints, and with panic_on_warn=1 it panics.

The transport __cxl_pci_mbox_send_cmd() already clamps the response copy
to min(out.size, payload_size, device len), so the output buffer is
never written beyond payload_size. Clamp the allocation to payload_size
too, matching the RAW path.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.